Two atavistic characters of some Lumbriculidae and their importance for the classification of Oligochaeta

The rudimentary atria, and the posterior sperm funnels and sperm ducts, which occur in some species of the Lumbriculidae, are discussed. It is shown that the posterior location of funnels and sperm ducts is the result of a forward shift of the atria, which refutes Stephenson's supposition that the Lumbriculidae is the most archaic family of the present-day Oligochaeta.     

鄱阳湖水生植被

本文列出了鄱阳湖98种水生维管束植物的名录,叙述了水生植被的分布。鄱阳湖水生植被面积为2262平方公里,占全湖总面积的80．8％。湖中植被呈不规则环带状分布,并可划分为湿生、挺水、浮叶和沉水4个植物带,9个主要植物群丛。并研究了鄱阳湖水生植被的演变及发展趋势和湖水位的季节性变化对植被的影响。     

鄱阳湖水生维管束植物生物量及其合理开发利用的初步建议

用4种不同的计算方法测定了鄱阳湖水生维管束植物的生物量。根据22个断面,199个采集点,398个样方的测定结果,得出鄱阳湖水生维管束植物的年生产量为431.76万吨(湿重),即相当于5.44×10~(-15)焦耳(能量)。其中,马来眼子菜、苦草和黑藻等3种合计约占总生物量的71.46%。全湖可供草食性鱼类食用的水生维管束植物约占总量的86.9%。文中还对4个植物带和9个群丛生物量的分布规律进行了讨论。提出了人工增殖草食性鱼类,调整湖中植被组成,保护和种植水生经济植物等合理开发利用鄱阳湖水生植物资源的初步建议。     

Density fluctuations in populations (1982–1986) and biological observations ofPotamopyrgus Jenkinsi in two trophically differing lakes

The hydrobiid snailPotamopyrgus jenkinsi (E.A. Smith), characterized by parthenogenesis and ovovivipary, was quantitatively sampled monthly between June, 1982, and December, 1986, on sandy bottoms in the shallow zones of the meso-oligotrophic Lake Maarsseveen I and the eutrophic Lake Maarsseveen II. The snail demonstrated a very clumped distribution in both lakes. The mean numbers of juveniles and adults taken together fluctuated strongly. Organisms in Lake I showed relatively high densities (up to 25,000 per m²) in 1982, followed by a sudden drop to values approaching zero in December, 1982, with a subsequent rapid increase in densities, fluctuating between 2,000 and 200 per m². In Lake II, densities of snails fluctuated between 13,000 and 300 per m² with decreases in the spring of 1985 and 1986. The various types of decreases in the lakes are extensively discussed, but no explanation is presently available. The reduction in Lake I was of catastrophic proportions, but the speed of recovery of the population was remarkable.Floating was observed only in Lake I, and only during the occurrence of the highest densities on the sediment. Burrowing behaviour was very common, but strongly suppressed under an uninterrupted dark regime. A shift of temperature from 15 to 22°C had the same effect. A number of submerged macrophyte species from Lake I proved to attractP. jenkinsi in the absence of sandy substrate, though these plants were only covered by the snail during the period of the highest densities in 1982. Temperatures of 20°C or lower were well tolerated, unlike temperatures of 25 and 30°C. Growth was distinct at 10, 15 and 20°C. Keeled individuals were encountered in much higher numbers in Lake I than in Lake II.     

Effects of stormwater sewer discharges on the aquatic community in urban canals in Lelystad

In urban areas with a separate sewerage system, the stormwater runoff is discharged into surface waters. A study on the effects of stormwater sewer discharges on the composition of the aquatic community in urban waters was carried out in two areas with a primarily residential use in the new town of Lelystad. The aquatic organisms considered included hydrophytes, epiphytic diatoms, filamentous algae and macroinvertebrates.The results indicate that the stormwater sewer discharges cause a slight change in the composition of the aquatic community. The water in the urban surface waters can be characterized as eutrophic and - toa-mesosaprobic. Near stormwater sewer outfalls the water tends to the more polluteda-mesosaprobic state. The shifts in the composition of the aquatic community could be traced primarily on the basis of a number of epiphytic diatoms and macroinvertebrates (in particular some Diptera and Trichoptera). Most hydrophytes, filamentous algae and the remaining epiphytic diatoms and macroinvertebrates (in particular water beetles and water mites) turned out to be of little or no use in this respect.Because the investigation was carried out in an unusually dry summer, the results probably underestimate the effects of stormwater discharges on the aquatic community.     

Introduction dans le Sud-Est de la france d'un parasite:Pauesia cedrobii [Hym.: Aphidiidae] du puceron:Cedrobium laportei [Hom.: Lachnidae] du cèdre de l'atlas:Cedrus atlantica

Résumé Le parasitePauesia cedrobii Stary et Leclant, spécifique du puceron du CèdreCedrobium laportei Remaudière, a été récolté dans le Moyen-Atlas, (Maroc) puis introduit dans un peuplement de cèdre (Cedrus atlantica Manetti) du sud-est de la France au printemps 1981. La méthode utilisée a consisté en une introduction directe des parasites, préalablement isolés sur le lieu de récolte (momies) puis mis à éclore en chambre climatisée de fa?on à éliminer les hyperparasites. Après accouplement, 225 adultes ont été introduits dans des manchons installés sur des rameaux abritant des colonies deC. laportei. L'évolution des populations de l'h?te et du parasite a été suivie au niveau des points de lacher d'une part, et dans la parcelle d'autre part. L'installation définitive du parasite dans la parcelle s'est produite, 1 an après le lacher, grace à un automne et à un hiver particulièrement doux, qui ont favorisé la multiplication de l'h?te. Le parasite est définitivement implanté: il est encore présent 4 années après le lacher. Entre temps, il a été étendu à d'autres forêts de cèdre du sud-est de la France. Huit espèces d'hyperparasites autochtones se sont portés surP. cedrobii, mais ceci ne remet pas en cause la réussite de l'introduction de l'aphidiide. Avec la collaboration technique deE. Robert, A. Chalon, J. Chizky.     

Insects on isolated colonies of common rock-rose Helianthemum chamaecistus

ABSTRACT.

• 1 A study was made of the insect species present on twenty-eight colonies of H.chamaecistus Mill, in 1978 ranging in size (cover) from 0.4 m² to about 6500 m² and separated from nearest large neighbours by distances up to 6.5 km. Twenty-three insect species were collected of which nine or ten were more or less monophagous.
• 2 There was a clear relationship between species richness and size of host colony. Sites with less than 30 m² of rock-rose, about 67% of those in the study area, were likely to have less than half of the monophagous species. Distance to neighbouring colonies did not contribute significantly to species richness.
• 3 The consistency of results from year to year was examined at five sites re-sampled in 1979. The 1978 data were also used to compare‘expected’and observed faunas at five new sites sampled in 1979 based upon the species-area relationship and the relative frequency of species at known sites.
• 4 Insect dispersal was examined using a suction trap placed near the largest rock-rose site. Colonization of new sites was studied by experimental outplanting of pot-grown plants.
• 5 These direct observations, and the monitoring of fourteen sites for 5 years, suggested that colonization and interchange of faunas were rare events. The experimental introduction of one to five species at four sites showed in several cases that the sites were suitable for the species, and that introduction could significantly enhance a site's complement.

     

农业生态系统中新物种引进的初步探讨

在现有的农业生态系统中,引进某些新物种,往往可以使整个系统的功能发生变化。如果新物种引进得当,则可产生良好的效果,系统功能得以改善,效益提高;反之,则会造成人力、物力、财力的损失,削弱系统的功能,甚至可能遗患无穷。因此,对农业生态系统中     

“引黄济青”输水沿线水生生物分布与蓄水库富营养化关系的研究

“引黄济青”是国家“七五”重点工程,由黄河下游博兴县境内打渔张闸引水,在渠首沉沙后,再经惠民、东营、潍坊和青岛的10个县区约253km的明渠输送,到达唠山县棘洪滩蓄水库蓄存,实现向青岛市日供水3.0×10~5m~3。明渠输水过程中,来白沿线的营养物质会污染水体,加之输水在库中滞留时间长,会不会发生富营养化,这是社会普遍关注的问题。     

An experimental demonstration of trophic interactions affecting water quality of Rice Lake, Ontario (Canada)

Eight cylindrical enclosures (3 m diameter, 2.7 m long, V = 20m³) were installed in eutrophic Rice Lake (Ontario, Canada) in late spring of 1987. Fish (yearling yellow perch (Perca flavescens) and macrophytes (Potamogeton crispus) presence and absence were set at the beginning of the experiment to yield four combinations of duplicate treatments. The purpose of the experiment was to determine if the phytoplankton, zooplankton, macrophytes and fish species resident in the lake interact to influence water quality (major ions, phosphorus, algal densities and water clarity).The presence of fish was associated with: (1) decreased biomass of total zooplankton, (2) decreased number of species in the zooplankton, (3) decreased average size of several zooplankton taxa, (4) higher total phosphorus concentrations, (5) higher phytoplankton and chlorophyll a concentrations, (6) lower water clarity, (7) lower potassium levels during macrophyte die-back, (8) lower pH and higher conductivity in the presence of macrophytes. Biomass of large Daphnia species (but not total zooplankton) was highly correlated with the algal response (r ² = 0.995) and was associated with reduced biomass of several algal taxa including some large forms (Mougeotia, Oedogonium) and several colonial blue-green algae. However, no significant control of late summer growth of the bloom-forming blue-green alga Anabaena planctonica Brun. was achieved by the Daphnia presence-fish absence treatment. Release of phosphorus to the water column during the die-back of P. crispus was not an important phenomenon.